Oxidant-induced lung injury induces widespread epithelial and endothelial injury and cell death together with airway inflammation, edema and hemorrhage. We have initiated an in-depth study of oxidative lung injury by proteomics. These studies show that oxidative stress results in impressive changes in the levels of specific proteins in the lung. These changes include a decline in the levels of proteins with anti-oxidant and anti-inflammatory properties. In our efforts to understand the mechanisms of oxidative injury and its protection, we have generated transgenic mice that inducibly express keratinocyte growth factor (KGF). Numerous studies have shown a protective role of KGF in oxidant-induced lung injury. In in vitro and in vivo studies of KGF-mediated protection, we have found that KGF protects lung epithelial cells from hyperoxia-induce death and induces the activation of the pro-survival Akt signaling axis both in vitro and in vivo. We have also demonstrated that expression of constitutively active Akt in the lung protects mice from hyperoxia-induced death. Using the yeast two-hybrid system, we have detected association of PAK4, a p21-activated kinase, with KGFR. Furthermore, the KGFR-PAK4 complex was also found to contain Raf-1. Both PAK4 and Raf-1 have been recently shown to promote cell survival. Our observations lead us to hypothesize that: 1) Oxidant-induced lung injury is the consequence of a disruption in protein balance in the lung, 2) KGF helps maintain the lung protein balance and 3) KGF-mediated protection involves activation of key pro-survival signaling mechanisms in target cells. To address our hypothesis we will: Aim I. Characterize the change in lung protein expression profile in animals subjected to hyperoxia in the presence or absence of activation of the KGF/FGFR2-IIIb axis. a) early and late markers of oxidative lung injury and b) effect of KGF-expression will be assessed by proteomics analysis of BAL fluid and lung extracts. Aim II. Investigate the protective role of specific signal transduction pathways that are induced upon activation of the KGF/FGFR2-IIIb axis in lung epithelial cells. The role of the signaling pathways, Akt, MAP kinase and PAK4-Raf-1 pathway in KGF-mediated protection from hyperoxia will be investigated using dominantnegative (DN) mutants of the molecules introduced into lung epithelial cells by adenovirus-mediated gone transfer. Aim 111. Investigate the role of specific signaling pathways that are induced by activation of FGFR2IIIb in protection from oxidative injury in vivo. Inducible transgenic mice expressing repressor of Akt, PTEN, DNPAK4 and p38B-/- mice will be crossed to KGF transgenic mice and the mice will be studied in a model of hyperoxic stress. Mice will be observed for lung pathology, cell death, Akt activation and cell proliferation.